Error analysis for semi-analytic displacement derivatives with respect to shape and sizing variables

Sensitivity analysis is fundamental to the solution of structural optimization problems. Consequently, much research has focused on the efficient computation of static displacement derivatives. As originally developed, these methods relied on analytical representations for the derivatives of the structural stiffness matrix (K) with respect to the design variables (b sub i). To extend these methods for use with complex finite element formulations and facilitate their implementation into structural optimization programs using the general finite element method analysis codes, the semi-analytic method was developed. In this method the matrix the derivative of K/the derivative b sub i is approximated by finite difference. Although it is well known that the accuracy of the semi-analytic method is dependent on the finite difference parameter, recent work has suggested that more fundamental inaccuracies exist in the method when used for shape optimization. Another study has argued qualitatively that these errors are related to nonuniform errors in the stiffness matrix derivatives. The accuracy of the semi-analytic method is investigated. A general framework was developed for the error analysis and then it is shown analytically that the errors in the method are entirely accounted for by errors in delta K/delta b sub i. Furthermore, it is demonstrated that acceptable accuracy in the derivatives can be obtained through careful selection of the finite difference parameter

The Economic Rationale for Agricultural Regeneration and Rural Infrastructure Investment in South Africa

This paper informs government policy insofar as it relates to the agricultural and rural development sectors and infrastructure investment within these sectors. The paper first quantifies the role of agriculture in the South African economy. This is done within the context of, inter alia, food security, agriculture’s contribution to gross domestic product (GDP), economic linkages and multipliers with respect to the agricultural sector, as well as agriculture’s employment creation and external stabilisation capacity. Investment in the agricultural and rural sectors are then analysed with a view of supporting the argument that agriculture’s role in the economy is sufficiently important to warrant regenerative strategies, including renewed emphasis on agricultural and rural infrastructure investment by South African policy makers. The quantification of the agricultural sector in relation to the total economy and that of agricultural and rural infrastructure investment are investigated against the backdrop of declining government support, increasing production risks due to a variety of exogenous events like climate change, and increasing dynamic trade impacts. In this paper, the authors offer both supporting arguments in terms of current economic policy and recommendations for more decisive policy measures aimed at agricultural regeneration and rural infrastructure investment.

Structure of ^112In nucleus

The γ-ray spectra of the ^112Cd(p,nγ)^112In and ^109Ag(α,nγ)^112In reactions were measured with Ge(Li) spectrometers for bombarding energies of 4.8 MeV protons and 17.1 MeV α particles. The energies and relative intensities of 79 ^112In γ-ray transitions have been determined. The electron spectra were measured with combined magnet plus Si(Li) as well as superconducting magnetic lens plus Si(Li) spectrometers. Internal conversion coefficients of 40 ^112In transitions have been determined, and the level scheme of ^112In, γ-ray branching ratios and transition multipolarities have been deduced. Computed Hauser-Feshbach (p,n) cross sections were compared with experimental ones, obtained from γ-ray measurements. On the basis of the internal conversion coefficients and Hauser-Feshbach analysis, level spins and parities have been determined. The energies of several ^112In proton-neutron multiplets were calculated on the basis of the parabolic rule derived from the cluster-vibration model. The level energy spectrum and electromagnetic properties were calculated on the basis of the interacting boson-fermion-fermion/odd-odd truncated quadrupole phonon model and satisfactory agreement was obtained between the experimental and theoretical results. More than 20 p-n multiplet states have been identified in ^112In

The current state-of-the-art of spinal cord imaging: methods.

A first-ever spinal cord imaging meeting was sponsored by the International Spinal Research Trust and the Wings for Life Foundation with the aim of identifying the current state-of-the-art of spinal cord imaging, the current greatest challenges, and greatest needs for future development. This meeting was attended by a small group of invited experts spanning all aspects of spinal cord imaging from basic research to clinical practice. The greatest current challenges for spinal cord imaging were identified as arising from the imaging environment itself; difficult imaging environment created by the bone surrounding the spinal canal, physiological motion of the cord and adjacent tissues, and small cross-sectional dimensions of the spinal cord, exacerbated by metallic implants often present in injured patients. Challenges were also identified as a result of a lack of "critical mass" of researchers taking on the development of spinal cord imaging, affecting both the rate of progress in the field, and the demand for equipment and software to manufacturers to produce the necessary tools. Here we define the current state-of-the-art of spinal cord imaging, discuss the underlying theory and challenges, and present the evidence for the current and potential power of these methods. In two review papers (part I and part II), we propose that the challenges can be overcome with advances in methods, improving availability and effectiveness of methods, and linking existing researchers to create the necessary scientific and clinical network to advance the rate of progress and impact of the research

Falagria Mannh. and Its Relatives

Volume: 20Start Page: 20End Page: 2

New Aleocharinae (Staphylinidae, Col.) of the U. S.

Volume: 20Start Page: 418End Page: 42

LAND TENURE: ATTITUDES IN LEBOWA

The land tenure system in Lebowa is similar to most traditional African systems. Both communal and individualised tenure have been advocated by different experts. A survey was conducted to determine the attitudes of Lebowa smallholders and leaders to land tenure systems. The majority of smallholders are in favour of change. The response from traditional leaders seems to be ambiguous. Both smallholders and non-traditional leaders favour more individualised tenure with more land being farmed by the better farmers. In general, there seems to be an interest in modernisation